This research will investigate the effects of maxilloficial surgery on the growth and adaptation of the craniofacial complex using Macaca fascicularis as experimental subjects. Mandibular growth following C-osteotomies to advance the mandible, with and without detachment of the suprahyoid muscles, will be studied histologically, histochemically, cephalometrically and using EMG. Relapse following total maxillary osteotomy and inferior repositioning of the maxila with autologous bonde grafts, with and without masseter myotomy, will be studied in both normal adult macaques and in a sample of macaques preadapted to a longer masseter muscle length. These subjects will be evaluated long-term using the techniques of EMG, bone strain analysis and roentgenographic cephalometrics. It is hypothesized that distracting muscle forces will have adverse short-term effects following mandibular advancement and adverse long-term effects following inferior maxillary repositioning. The results of these studies will have a direct and immediate impact on the related clinical problems of early maxillofacial surgical intervention and long-term (i.e., relapse) of surgical result.